/usr/bin/aarch64-linux-gnu-gfortran is in gfortran-aarch64-linux-gnu 4:6.3.0-4.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/bin/aarch64-linux-gnu-gfortran-6
/usr/bin/aarch64-linux-gnu-gfortran-6